Transactinoid elements transactinoids

Fig. 1.1 Volatile compounds and elemental forms characteristic of the lighter homologs of transactinoid elements.

Figure 1.1 shows some volatile compounds formed by the common elements of groups 4 to 11, as well as the relatively volatile metals of groups 12 to 14. The compounds of transactinoid elements with supposedly similar stoichiometry have been studied in works reported by now. A few studies have also been done with bromides and oxybromides. 

Elements from Re to Pt are the expected homologs of elements 107 to 110. Chemistry of the halides in these groups is rather complicated it is difficult to reveal any regularity which would allow reasonable extrapolations to the transactinoids. Meanwhile, the above closest congeners show an unexpected common behavior. In the TC experiments with either dry or moist air as a carrier gas, the tracer quantities of Re and platinum metals deposited at surprisingly low temperatures [53]. It indicated formation of gaseous oxides and hydroxides, which were mentioned above in this section. This group property is very specific and allows easy separation from the... 

Production of Transactinoid Elements, Synthesis and Transportation of Compounds... 

One of the basic requirements is to synthesize the desirable compounds and to rapidly transport them to the equipment for chemical experiments. The time spent to accomplish such processes and its probability distribution can be properly determined only when a radioisotope of the element under study can be produced in a quantity that can be easily and accurately measured. It has never been the case for the transactinoid elements. Rough estimation of the chlorination time of Zr and Mo was done in the model experiments described in the above Section (see also Fig. 1.2). The ampoule was filled with pure inert gas, then closed and bombarded for some time with neutrons at ambient temperature. Thus, the thermalized fission products were accumulated on the walls. Then the ampoule was heated and flushed for a short time with the gas containing a reagent. Most of the activity got transferred into the nap in 30 seconds or so it involved a mean gas hold-up time of 15 seconds, so that the actual upper limit of the chlorination time could be set as 15 seconds. 

Unfortunately, in the continuous on-line experiments with transactinoid elements, the application of the above Second Law and related procedures has not been possible because of the very poor statistics of detected decays. Measurements of this type have been done only with long-lived lighter homologs of the transactinoids in batch tests. Packed columns and low flow rates of the carrier gas were employed to achieve narrow peaks. Major contribution came from Bachmann and co-workers. In Refs. [6,9-11] they measured the adsorption enthalpies and entropies on solid... 

Typically the experiment with a transactinoid element lasts days or even weeks, and results in a single experimental value of the adsorption constant. The only possibility to obtain an estimate of the adsorption enthalpy based on such a result is to calculate the entropy change from the first principles [4] and substitute it into Eq. 5.7. The values of Aa( sS are calculated from the formulae of statistical mechanics for the particular model of the adsorbed state. The evaluation starts with the partition function of single molecule qm and with the molar partition function Z to calculate the absolute molar entropy from the general equation ... 

In the meantime, the whole field of transactinoid studies, with its peculiar and nontrivial features, is still young — if not by years since birth, then by the number of experiments performed to date. The major motivation — the quest for still new elements and demands for their chemical identification — greatly stimulated the development of the experimental instruments and techniques. In the first place, these were high efficiency spectroscopic low-level measurements of the particle radioactivity of short-lived nuclides in the specific conditions of chemical experiments. Necessarily, the fundamental chemical and physicochemical problems behind the employed methods, as well as evaluation of uncertainties of the results, have not been paid adequate attention. Much more could be learned (but was not) in off-line studies of long-lived radioisotopes of common elements with good statistics. As a result, some conclusions in the literature are not well founded, and important details of the experimental conditions are not given. 

From the early studies of gas-phase chemistry of transactinoids, the experimenters have faced the question of whether the ultimately low number of short-lived atoms would bring new fundamental problems in obtaining reliable data and their interpretation. Classical radiochemistry dealt mostly with aqueous solutions and widely used batch realization of the partition methods, like coprecipitation or extraction. The goal was to find known element(s) with chemical behavior like the new radionuclide, at least in some particular chemical systems the homology was then used for isolation, concentration and assignment of the chemical state of the activity. Researchers in the field occasionally noted some peculiar, even erratic behavior of the tracer elements. At first, these observations might hardly be rationalized later,... 

My sincere thanks go to my colleagues V. Z. Belov, Yu. T. Chuburkov, V. P. Domanov, B. Eichler, S. Hiibener, M. R. Shalaevskii, L. K. Tarasov, A. B. Yakushev, B. L. Zhuikov, T. S. Zvarova - my wife, and others. Together we pioneered and conducted transactinoid studies as well as tried to analyze the fundamental aspects of what we were doing - the gas phase radiochemistry of metallic elements. We were a small group of chemists embedded in a large physical laboratory. Hence, it was of decisive importance for us that the late Prof. G. N. Flerov put much emphasis on the role of chemical identification of new elements. He actually initiated, and then invariably supported, radiochemical studies in the Dubna laboratory. 

Chapter 1 presents some details of the experimental developments which were important steps forward. It also briefly describes a few typical concrete studies of the transactinoid elements. The emphasis is on novel approaches, techniques and classes of the utilized compounds, as well as on posing and solving problems. Consistently, the presentation tends to comply, if possible, with both the historical and logical sequences of the events. Closing sections of the chapter consider various classes of inorganic compounds, other than the widespread chlorides, as to their prospects for future studies. 

Table 1.1 Place of the Transactinoid/Superheavy Elements in the Mendeleev Periodic Table of the Elements. Emphasized are the calculated and just expected ground state electronic configurations...

Transuranium, transplutonium, (and so forth) elements are essentially all elements with atomic numbers higher than that specified by the name no upper limit is implied. In the meantime, for what are essentially translawrencium elements, the radiochemical community uses the improper term transactinoid elements (TAEs). Nevertheless, we will stick to the latter because it emphasizes that, after a long row of elements of the actinoid character, one again deals with -elements, each of which must have distinct individual chemistry. 

Identify the starting isotopes A-E in each of the following syntheses of transactinoid elements ... 

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